Create Trie1.cpp

Author: TheSYNcoder

Topic/Solution/Trie1.cpp

@@ -0,0 +1,64 @@
+class Solution {
+public:
+    
+    struct trie{
+        trie* next[26];
+        int end; 
+    };
+    void insert( string word , trie* root ){
+        for ( char c : word){
+            if ( !root->next[c-'a'] ) root->next[c-'a'] = new trie();
+            root = root->next[c-'a'];
+        }
+        root->end =1;
+    }
+    
+    void rec( vector<vector<int>> &vis , vector<vector<char>> &board , int x , int y , trie* root ,string curr, set<string> &ans ){
+        
+        int n = board.size();
+        int m = board[0].size();
+        
+        // base condition for return 
+        if (x < 0 || y < 0 || x >= n || y >= m ) return ;
+        // already done in current recursion
+        if ( vis[x][y] ) return;
+        // if no such word exists it is useless to recurse
+        if (!root ||  !root -> next[board[x][y] - 'a']) return ;
+       
+        root = root -> next[board[x][y]-'a'];
+        curr.push_back(board[x][y]);
+        if ( root->end == 1)
+            ans.insert(curr);
+            //however we still don't end recursion for words like "end" and "ending"
+        
+        vis[x][y] =1;
+        rec( vis , board , x + 1, y , root ,curr , ans);
+        rec( vis , board , x - 1, y , root ,curr , ans);
+        rec( vis , board , x , y -1, root ,curr  ,ans);
+        rec( vis , board , x , y +1 , root ,curr , ans);
+        vis[x][y] =0;
+        curr.pop_back();
+        
+    }
+    
+    
+    
+    vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
+        trie * root = new trie();
+        for ( string word  : words) { 
+            insert( word ,  root);
+        }
+        set<string> ans; 
+        string curr;
+        int n = board.size();
+        int m = board[0].size();
+        vector<vector<int> > vis( n , vector<int> ( m , 0 ));
+        for ( int i =0 ; i < n ;  i++ )
+            for ( int j = 0 ; j < m ;  j++) 
+                rec( vis ,board,  i , j , root ,curr, ans);
+        vector<string> ret;
+        for ( string a : ans)
+            ret.push_back(a);
+        return ret;
+    }
+};